Key facts
- Foundayo (orforglipron) is a once-daily GLP-1 tablet; Zepbound (tirzepatide) is a once-weekly GIP and GLP-1 injection. Both are made by Eli Lilly.[1][3]
- In separate 72-week trials, the top dose of Foundayo gave 11.2% mean weight loss (ATTAIN-1) and Zepbound 15 mg gave 20.9% (SURMOUNT-1).[5][6]
- Nausea on the labels: 26% to 35% on Foundayo (placebo 10%) and 25% to 29% on Zepbound (placebo 8%), in separate pooled trials.[1][3]
- Lilly self-pay: Foundayo $149 to $349 a month by dose; Zepbound vials or KwikPen $299 to $699, or $449 for 7.5 mg and up with a refill within 45 days.[13][14]
- No head-to-head trial of orforglipron against tirzepatide has been published or registered as of 8 November 2026.[11]
Foundayo vs Zepbound at a Glance
Foundayo is a daily pill that gave 11.2% weight loss at 72 weeks and costs $149 to $349 a month self-pay, while Zepbound is a weekly injection that gave 20.9% at 72 weeks and costs $299 to $699 a month self-pay.[5][6][13][14]
| Feature | Foundayo (orforglipron) | Zepbound (tirzepatide) |
|---|---|---|
| Form | Tablet by mouth, swallowed whole[1] | Injection under the skin: single-dose pen, single-dose vial, multi-dose vial or KwikPen[3] |
| Frequency | Once daily, with or without food[1] | Once weekly, any time of day, with or without meals[3] |
| Receptor(s) | GLP-1 receptor only[1] | GIP and GLP-1 receptors[3] |
| Doses | 0.8, 2.5, 5.5, 9, 14.5 and 17.2 mg; maximum 17.2 mg a day[1] | 2.5 mg start, then 5, 7.5, 10, 12.5 and 15 mg; maintenance 5, 10 or 15 mg; maximum 15 mg a week[3] |
| Best weight result | -11.2% at 72 wk, top dose, ATTAIN-1 (placebo -2.1%)[5] | -20.9% at 72 wk, 15 mg, SURMOUNT-1 (placebo -3.1%)[6] |
| Nausea, pooled weight trials | 26% to 35% by dose vs 10% placebo[1] | 25% to 29% by dose vs 8% placebo[3] |
| Self-pay price (Lilly) | $149 to $349 per 30 days[13] | $299 to $699 per 28 days (vial or KwikPen)[14] |
| US approval for weight | 1 April 2026[2] | 8 November 2023[4] |
| Other approved uses | None in the US as of Nov 2026[1] | Moderate to severe obstructive sleep apnoea in adults with obesity[3] |
Neither Foundayo nor Zepbound is sold in this shop, and this page is not a guide to obtaining either. It summarises FDA labels, published trials and Lilly’s public pages for reference.
Foundayo vs Zepbound: Key Differences
Foundayo is a small, non-peptide molecule taken daily with a half-life of about 29 to 49 hours, while Zepbound is a peptide injected weekly with a half-life of about 5 days that acts on GIP as well as GLP-1 receptors.[1][5][3]
- Hormone targets. Foundayo binds to and activates the GLP-1 receptor. Tirzepatide binds to and activates both the GIP and GLP-1 receptors, and the Zepbound label says nonclinical studies suggest the added GIP action may further help regulate food intake.[1][3]
- Molecule. Orforglipron is a small-molecule, non-peptide drug, which is why it works as a pill. Tirzepatide is a peptide carrying a C20 fatty diacid that binds albumin and stretches its half-life.[5][3]
- Dose steps. Foundayo starts at 0.8 mg and moves up after at least 30 days on each dose, through 2.5 mg and 5.5 mg, then optionally to 9, 14.5 or 17.2 mg. Zepbound starts at 2.5 mg for 4 weeks and rises in 2.5 mg steps at least 4 weeks apart.[1][3]
- Missed doses. For Foundayo, take a missed dose as soon as possible but never double up; after 7 or more missed doses in a row, escalation restarts at a lower dose. For Zepbound, a missed dose can be given within 4 days, otherwise it is skipped.[1][3]
- Interactions. Only the Foundayo label caps the dose with a strong CYP3A4 inhibitor (9 mg a day) and limits simvastatin to 20 mg a day. Both labels warn that slower stomach emptying may affect oral contraceptives: 30 days of backup after starting or a dose rise for Foundayo, 4 weeks for Zepbound.[1][3]
Both labels say not to combine the drug with another GLP-1 receptor agonist, so Foundayo and Zepbound are not meant to be used together.[1][3] For the full orforglipron profile, see what is orforglipron.
Has Orforglipron Been Tested Against Tirzepatide?
No. None of the 54 orforglipron studies on ClinicalTrials.gov on 8 November 2026 uses tirzepatide as a comparator, and a PubMed search found no published head-to-head trial of the two.[11]
- Closest study: ATTAIN-MAINTAIN. It moved people from Zepbound or Wegovy to orforglipron and compared orforglipron with placebo, not with continued Zepbound. The authors list the lack of a continued-injection arm as a limitation.[7]
- Only head-to-head phase 3 so far: ACHIEVE-3. Orforglipron was compared with oral semaglutide in 1,698 adults with type 2 diabetes, where 36 mg lowered HbA1c by 1.91 points against 1.47 for semaglutide 14 mg at 52 weeks.[10]
- What this means. Any Foundayo vs Zepbound comparison of weight loss or side effects comes from separate trials with different populations, so the gap between them is an estimate, not a measured difference.
Foundayo vs Zepbound Weight Loss
In separate 72-week trials of adults without diabetes, the top dose of Foundayo gave 11.2% mean weight loss in ATTAIN-1 (placebo 2.1%) and Zepbound 15 mg gave 20.9% in SURMOUNT-1 (placebo 3.1%).[5][6]
Treatment-regimen estimand from each NEJM abstract. ATTAIN-1 top dose was 36 mg of the trial capsule, shown on the label as 17.2 mg. Not a head-to-head comparison.
| Trial | Population | Doses | Mean weight change | Placebo |
|---|---|---|---|---|
| ATTAIN-1 (Foundayo, n = 3,127) | Obesity or overweight, no diabetes | 6, 12, 36 mg capsule (5.5, 9, 17.2 mg tablet) | -7.5%, -8.4%, -11.2% | -2.1%[5][1] |
| SURMOUNT-1 (Zepbound, n = 2,539) | Obesity or overweight, no diabetes | 5, 10, 15 mg | -15.0%, -19.5%, -20.9% | -3.1%[6] |
| ATTAIN-2 (Foundayo, n = 1,613) | Obesity or overweight with type 2 diabetes | 5.5, 9, 17.2 mg | -5.1%, -7.0%, -9.6% | -2.5%[1] |
| SURMOUNT-2 (Zepbound, n = 938) | Obesity or overweight with type 2 diabetes | 10, 15 mg | -12.8%, -14.7% | -3.2%[3] |
- At least 20% weight loss: 18.4% on the top Foundayo dose in ATTAIN-1 (placebo 2.8%), against 57% on Zepbound 15 mg in SURMOUNT-1 (placebo 3%).[5][6]
- Lilly reports that people on the top Foundayo dose who stayed on treatment lost 12.4% (27.3 lb), against 0.9% on placebo.[12]
- Both trials ran 72 weeks with diet and activity counselling, but ATTAIN-1 enrolled more Asian participants (28% against 11%), and the trials ran years apart with different dose schedules.[1][3]
- The labels note that weight loss was seen regardless of age, sex, race, ethnicity, baseline BMI and glycaemic status in both programmes.[1][3]
Foundayo vs Zepbound Side Effects
Nausea affected 26% to 35% of people on Foundayo (placebo 10%) and 25% to 29% on Zepbound (placebo 8%), and 6% to 10% stopped Foundayo because of adverse reactions against 4.8% to 6.7% for Zepbound, in each drug’s pooled 72-week weight trials.[1][3]
| Adverse reaction | Foundayo 5.5 / 9 / 17.2 mg | Foundayo placebo | Zepbound 5 / 10 / 15 mg | Zepbound placebo |
|---|---|---|---|---|
| Nausea | 26% / 34% / 35% | 10% | 25% / 29% / 28% | 8% |
| Diarrhoea | 21% / 23% / 25% | 11% | 19% / 21% / 23% | 8% |
| Vomiting | 13% / 21% / 24% | 4% | 8% / 11% / 13% | 2% |
| Constipation | 20% / 27% / 24% | 9% | 17% / 14% / 11% | 5% |
| Any GI adverse reaction | 60% / 68% / 69% | 37% | 56% / 56% / 56% | 30% |
| Stopped due to any adverse reaction | 6% / 9% / 10% | 3% | 4.8% / 6.3% / 6.7% | 3.4% |
| Stopped due to GI reactions | 3% / 6% / 6% | 0.7% | 1.9% / 3.3% / 4.3% | 0.5%[1][3] |
- Boxed warning. Both carry the thyroid C-cell tumour boxed warning and are contraindicated with a personal or family history of medullary thyroid carcinoma or MEN 2. Tirzepatide caused C-cell tumours in rats; orforglipron is not active in rats or mice and caused none.[1][3]
- Heart rate. Mean heart rate rose 4 to 5 beats per minute on Foundayo (placebo 0.5) and 1 to 3 beats per minute on Zepbound (no rise on placebo).[1][3]
- Pancreatitis. Confirmed acute pancreatitis ran at 0.14 per 100 patient-years on Foundayo (placebo 0.04) and 0.14 on Zepbound (placebo 0.15) in the pooled weight trials.[1][3]
- Injection-site reactions. These apply to Zepbound only: 6% to 8% against 2% on placebo.[3]
- Shared warnings. Both labels warn on severe GI reactions, kidney injury from dehydration, gallbladder disease, low blood sugar with insulin or sulfonylureas, hypersensitivity, diabetic retinopathy in type 2 diabetes and aspiration during anaesthesia. The Zepbound label removed its suicidal behaviour warning in February 2026, and the Foundayo label has none.[1][3]
In both labels, nausea, vomiting and diarrhoea were most common while the dose was being raised and decreased over time.[1][3] For the full Foundayo list, see Foundayo side effects.
Foundayo vs Zepbound Price
Lilly’s regular self-pay price is $149 to $349 per 30 days for Foundayo and $299 to $699 per 28 days for Zepbound vials or KwikPen, and both are listed at $50 a month for eligible Medicare Part D patients, on Lilly’s pages checked 8 November 2026.[13][14][15]
| Step | Foundayo dose and regular price | Zepbound dose and regular price |
|---|---|---|
| Starting dose | 0.8 mg: $149 | 2.5 mg: $299 |
| Second step | 2.5 mg: $199 ($149 to 31 Dec 2026) | 5 mg: $399 |
| Third step | 5.5 mg: $299 ($199 to 31 Dec 2026) | 7.5 mg: $499 ($449 with refill within 45 days) |
| Higher doses | 9 mg: $299 | 10 mg and 12.5 mg: $699 ($449 with refill within 45 days) |
| Top dose | 14.5 mg and 17.2 mg: $349 ($299 with refill within 45 days)[13] | 15 mg: $699 ($449 with refill within 45 days)[14] |
- Commercial insurance. With coverage for Foundayo, the savings card brings the cost to as little as $25. For Zepbound, the $25 card price applies to the single-dose Pen, not the vial or KwikPen.[13][15]
- Medicare GLP-1 Bridge. Lilly lists Foundayo at $50 a month and Zepbound at no more than $50 a month for eligible Part D patients prescribed them for weight management, and says neither is a guarantee of coverage.[13][15]
- Expiry. Both self-pay cards end on 31 December 2026, and Lilly can change the offers at any time.[13][14]
For dose-by-dose Foundayo pricing and the savings card rules, see Foundayo price.
Who Each Was Studied In
Foundayo’s main obesity trial enrolled 3,127 adults without diabetes (mean BMI 37, mean weight 103.2 kg), and Zepbound’s enrolled 2,539 adults without diabetes (mean BMI 38, mean weight 104.8 kg).[1][3]
| Trial | n | Mean age | Female | Asian | Mean weight | Mean BMI |
|---|---|---|---|---|---|---|
| ATTAIN-1 (Foundayo, no diabetes) | 3,127 | 45 | 64% | 28% | 103.2 kg | 37[1] |
| SURMOUNT-1 (Zepbound, no diabetes) | 2,539 | 45 | 68% | 11% | 104.8 kg | 38[3] |
| ATTAIN-2 (Foundayo, type 2 diabetes) | 1,613 | 57 | 47% | 17% | 101.4 kg | 35.6[1] |
| SURMOUNT-2 (Zepbound, type 2 diabetes) | 938 | 54 | 51% | 13% | 100.7 kg | 36.1[3] |
- All four trials enrolled adults with a BMI of 30 or more, or 27 or more with at least one weight-related condition, and gave everyone diet and activity counselling.[1][3]
- The diabetes trials of both drugs excluded people already taking GLP-1 receptor agonists or DPP-4 inhibitors, and people on insulin.[1][3]
- The Zepbound label also covers a trial with a 12-week intensive lifestyle lead-in, a randomised withdrawal trial, and two obstructive sleep apnoea trials.[3]
- Both labels state that safety and effectiveness have not been established in children.[1][3]
Switching From Zepbound to Foundayo
Neither FDA label gives instructions for switching between the two, but in Lilly’s ATTAIN-MAINTAIN trial, 205 people who switched from Zepbound to orforglipron kept 74.7% of their earlier weight loss at 52 weeks, against 49.2% on placebo.[1][3][7]
- Who took part. Participants came from SURMOUNT-5, where they had used Zepbound 10 or 15 mg or Wegovy 1.7 or 2.4 mg for 72 weeks and reached a weight plateau, defined as less than 5% change between weeks 60 and 72.[8]
- How the switch was done. Orforglipron started at 12 mg of the trial capsule and rose every 4 weeks to 36 mg or the maximum tolerated dose (24 or 36 mg). Anyone who regained 50% or more of their earlier loss was given rescue orforglipron.[8]
- Weight in kilograms. Lilly reports that people who switched from Zepbound averaged 90.9 kg at the switch and 95.9 kg after 52 weeks, keeping all but 5.0 kg of their loss. Those who switched from Wegovy kept all but 0.9 kg.[9]
- Side effects after the switch. Nausea affected 18.8% on Foundayo against 4.1% on placebo, and 7.2% of those switched from Zepbound stopped because of adverse events (placebo 6.3%).[9]
- Staying on Zepbound instead. In Lilly’s SURMOUNT-MAINTAIN trial, people who stayed on their maximum tolerated Zepbound dose kept all of their earlier loss over a further year, and those who dropped to 5 mg kept all but 5.6 kg.[9]
ATTAIN-MAINTAIN had no arm that stayed on Zepbound, so it shows that orforglipron beat placebo after a switch, not that it matches continued tirzepatide.[7] Lilly has not published any data on moving the other way, from Foundayo to Zepbound. Stopping treatment altogether led to regain in Zepbound’s withdrawal trial: weight rose 14.0% on placebo over 52 weeks, against a further 5.5% loss on Zepbound.[3]
Frequently Asked Questions
Is Foundayo as effective as Zepbound?
Not on the published numbers. In separate 72-week trials, the top dose of Foundayo gave 11.2% average weight loss in ATTAIN-1 and Zepbound 15 mg gave 20.9% in SURMOUNT-1. No trial has compared the two directly, so the gap is an estimate.
Is Foundayo cheaper than Zepbound?
On Lilly’s self-pay prices, yes. Foundayo is $149 to $349 for 30 days depending on dose, while Zepbound vials or KwikPen are $299 to $699 for 28 days, or $449 for 7.5 mg and above with a refill within 45 days. Both are listed at $50 a month for eligible Medicare Part D patients.
Can you switch from Zepbound to Foundayo?
Lilly has tested it. In ATTAIN-MAINTAIN, people who had plateaued on Zepbound and switched to orforglipron kept 74.7% of their earlier weight loss at one year, against 49.2% on placebo, regaining 5.0 kg on average. Neither label gives switching instructions, so this is a decision for the prescriber.
Has orforglipron been tested against tirzepatide?
No. As of 8 November 2026, no head-to-head trial of orforglipron against tirzepatide has been published, and none of the 54 orforglipron studies on ClinicalTrials.gov uses tirzepatide as a comparator.
Which causes more nausea, Foundayo or Zepbound?
The label rates are close but come from separate trials: 26% to 35% on Foundayo against 10% on placebo, and 25% to 29% on Zepbound against 8% on placebo. Vomiting was higher on Foundayo (13% to 24%) than on Zepbound (8% to 13%).
Is Foundayo just Zepbound in pill form?
No. They are different molecules. Foundayo contains orforglipron, a small-molecule drug that activates the GLP-1 receptor only. Zepbound contains tirzepatide, a peptide injected weekly that activates both GIP and GLP-1 receptors. Both labels say not to take them together.
Sources
- FDA. FOUNDAYO (orforglipron) tablets prescribing information, revised 07/2026 (NDA 220934, supplement 3)
- FDA. Drugs@FDA, NDA 220934 (Foundayo) approval history
- FDA. ZEPBOUND (tirzepatide) injection prescribing information, revised 08/2026 (NDA 217806, supplement 41)
- FDA. Drugs@FDA, NDA 217806 (Zepbound) approval history
- Wharton S, et al. Orforglipron, an oral small-molecule GLP-1 receptor agonist for obesity treatment (ATTAIN-1). N Engl J Med 2025;393(18):1796-1806. DOI 10.1056/NEJMoa2511774
- Jastreboff AM, et al. Tirzepatide SURMOUNT-1. N Engl J Med 2022;387:205-216. DOI 10.1056/NEJMoa2206038
- Aronne LJ, et al. Orforglipron for maintenance of body weight reduction (ATTAIN-MAINTAIN). Nature Medicine 2026;32(7):2679-2687. DOI 10.1038/s41591-026-04386-7
- Eli Lilly press release, 18 Dec 2025: ATTAIN-MAINTAIN topline results
- Eli Lilly press release, 12 May 2026: ATTAIN-MAINTAIN and SURMOUNT-MAINTAIN results (ECO 2026)
- Rosenstock J, et al. Once-daily oral orforglipron compared with oral semaglutide in type 2 diabetes (ACHIEVE-3). The Lancet 2026;407(10534):1147-1160. DOI 10.1016/S0140-6736(26)00202-3
- ClinicalTrials.gov, studies with orforglipron (LY3502970) as an intervention, 54 records, searched 8 Nov 2026
- Eli Lilly press release, 1 Apr 2026: FDA approves Foundayo (orforglipron)
- Lilly, Foundayo coverage and savings page with savings card terms (page code CMAT-27550 08/2026, checked 8 Nov 2026)
- Lilly, Zepbound self-pay vial and KwikPen terms and conditions (page code CMAT-26402 09/2026, checked 8 Nov 2026)
- Lilly, Zepbound savings page (page code CMAT-26402 09/2026, checked 8 Nov 2026)
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